Gels of mixed chromium and aluminium oxides were prepared by hydrolysis and polycondensation of organic precursors of metals. In this work, we try to understand the chemistry involved in the preparation, to better control the formation of final material. Evolution of UV-vis, ESR and IR spectra with stirring time, shows a modification of the environment of Cr3+ ions assigned to the formation of Cr[(acac)Al(O-Bu)3]3 complex. The rise of chromium amount or acetic acid reduces the gelation rate, whereas an extent of aging time favors the gelation.
L. Barakat, A. Ghorbel
sol-gel, chromium, UV-Visible, ESR, IR